Teenage boys with behavior problems may be able to blame their brain chemistry, according to a new study. Psychologists studied boys with a history of antisocial behavior and measured their levels of the hormone cortisol, which usually surges during stressful situations, causing people to focus and behave more cautiously. They found that the troubled boys didn’t have the normal cortisol spike when they were put under stress, suggesting that they weren’t getting a chemical signal to regulate their emotions and actions.

Researchers say the findings suggest that some bad behavior should be considered a form of mental illness. “Most research has looked at social factors like peer groups, family life and socioeconomic factors,” said [lead researcher] Graeme Fairchild…. “These findings basically indicate that antisocial behavior is probably more biologically based than many people recognize and is similar to conditions like depression and anxiety” [Reuters].

In the study, researchers assembled a control group of 100 teenage boys and a group of 75 boys with a history of aggressive behavior; all the boys were shown to have similar cortisol levels before the experiment started. The study pitted each volunteer against a pugnacious, virtually generated rival boy in a computer game that had them competing for a monetary reward. The game was deliberately rigged to subject volunteers to stress, frustration, provocation, and taunting from their adversary [New Scientist]. Researchers took saliva samples from all the volunteers and found that control subjects’ cortisol levels went up during the game, while the volunteers with behavior problems had a drop in cortisol levels.

The study, published in the journal Biological Psychiatry, may point the way towards eventual medical treatments for antisocial behavior. Says Fairchild: “A possible treatment for this disorder offers the chance to improve the lives of both the adolescents who are afflicted and the communities in which they live” [BBC News].